The present invention relates to an explosive powder charge operated setting tool suitable for setting bolts.
Non-repeating setting tools operated by an explosive power charge are known for instance from the published European Patent Application No. 0,233,740, in which the combustion gases, which are produced after firing the cartridge containing the explosive power charge, are used to guide the piston back into the starting position. In order to conduct the combustion gases into the space between the piston head and barrel, so that they form here a combustion-gas cushion which presses the piston back into its starting position after the bolt has been fired, complicated gas bypasses having valves and seals have been provided. The ability of said valves to function is moreover adversely affected by combustion residues which are entrained by the combustion gases. In this case, because of the seal-tightness required, a series of parts have to be manufactured with great accuracy.
The setting tool known from the published European Patent Application No. 0,638,395 also uses the combustion gases to guide back the piston into its starting position. The combustion gases are guided via a valve device into a storage space wherein the combustion gases are compressed. To control this, the barrel consists of two parts which are relatively close to each other in the direction of their axis. This solution also provides the drawbacks that on one hand the combustion gases are used to guide the piston back into its starting position so that combustion residues may cause problems, and that on the other hand this requires a relatively complicated construction which is not completely shown in the drawings of this application.
Additionally, the published European Patent Application No. 0,798,084 describes a setting tool using combustion gases and a slot valve system for guiding back the piston into its starting position.
Further, U.S. Pat. No. 2,877,750 deals with a buffer mechanism for a setting tool to prevent the piston from overworking. The buffering of the piston is achieved by conducting combustion gases into a buffer zone in moving direction of the piston before the latter so that the combustion gases are compressed to effect the deceleration of the piston.